1. Field of the Invention
The present invention relates to a method of operating an upsetting press for reducing the width of a hot slab cast in a continuous casting plant by laterally pressing the slab between the pressing tools of the upsetting press which are moved toward each other and away from each other by means of an eccentric lifting member as the slab moves on a roller conveyor through the upsetting press.
2. Description of the Related Art
Upsetting presses for reducing the width of continuously cast slabs are known. They are used in order to be able to carry out a rolling schedule which is as varied as possible with the smallest number of slab widths as possible. It has been found that the adjustment of adjustable molds in continuous casting plants for manufacturing slabs of differing widths is too slow and too complicated. It has further been found that the lateral upsetting of a hot continuously cast slab between the rolls of heavy vertical stands in many cases does not lead to the expected success because for technological reasons the slab material bulges in the edge region during edging rolling, and during flat rolling tongue-like portions are formed at the front end of the rolled strip and fishtail-like portions are formed at the end of the strip.
The lateral upsetting of a hot slab between the pressing tools of an upsetting press has the advantage that the slab material is upset far to the center of the slab, so that edge bulges occurring during edging rolling are almost completely eliminated and the formation of fishtail-like portions at the slab ends and, thus, also at the ends of the hot-rolled strip, is significantly reduced as compared to edging rolling in a vertical stand. As a result, the slabs upset in the upsetting press have an almost rectangular cross-section. Since the slab ends are well-formed and the slab cross-section is also well-formed, there is a smaller amount of hot top discard in the subsequent rolling mill train than in the past. This increases the yield of the entire rolling plant. In addition, because of the relatively long length of engagement of the pressing tools, upsetting ensures slab edges which are shaped in an optimum manner. For example, by means of an upsetting press known from European patent application 0 400 385 A2, the width of a hot continuously cast slab could be reduced in one pass by up to 300 mm. In other words, the upsetting press represents a highly effective deformation stage in front of the hot rolling mill.
The upsetting press for reducing the width of rolled material, particularly for reducing the width of slabs, in hot-rolled wide strip breaking-down trains in accordance with European patent application 0 400 385 A2 shown in FIG. 1 of the attached drawing, has on both sides tool carriers 2 which are arranged at the slab edge and receive pressing tools 1 which face toward each other. The reduction drive for each pressing tool is a lever system 4 which is actuated by a crank drive 3 and is movable essentially in direction of the reduction. The crank drive is arranged in a crank housing 5 which is arranged in a press frame 6 so as to be adjustable relative to the width of the slab. A feed drive 9 which operates essentially in direction of slab feeding direction 8 acts on the tool carrier which receives the pressing tool. The feed drive is constructed as a hydraulic piston-cylinder unit which is movable in accordance with a distance/time function and which facilitates the synchronization of the pressing tool with the moved slab in dependence on the desired feeding distance. In other words, the feeding distance of the pressing tools is adjusted in an optimum manner to the continuous travel speed of the slab through the press. If the preselection of the feeding speed is 0, the upsetting press automatically changes over to stop-and-go operation. In stop-and-go operation, no feeding takes place, i.e., the slab rests on the roller conveyor during the upsetting step. The slab is only conveyed further after the pressing tools have been moved away from the slab edge.